Server based communication services such as the Messenger service provided by MSN® communication services permit users to sign into a server-based network and then use the services of the network (e.g., e-mail, text messaging, etc.). A server may store a contact list for the user and the user can add and delete persons from the contact list. When the user signs in, a server or servers may notify persons in the user's contact list that the user is “online.” Similarly, the server or servers may notify the user of persons in the user's contact list that are “online.”
The MICROSOFT® Corporation also provides Peer-to-Peer Networking software for use with its WINDOWS® operating systems. With this system, users can create a network of peer computers and can communicate with one another without having to sign into a central server. For example, users can create a peer-to-peer group and then create a chat room in which all members of the group can post messages and see messages posted by others in the group. The system may also allow peers to invite others to participate in collaborative activities. The chat room is maintained using the peer computers and without the need for a central server.